Modern turbines often operate at extremely high temperatures. The effect of temperature on the turbine blades and/or stator vanes can be detrimental to the efficient operation of the turbine and can, in extreme circumstances, lead to distortion and possible failure of the blade or vane. In order to overcome this risk, high temperature turbines may include hollow blades or vanes incorporating so-called impingement devices for cooling purposes.
These impingement devices e. g. so-called impingement plates or impingement tubes are perforated thin wall structures often made of sheet metal that covers surfaces of the blades or vanes that face the opposite side of the wall of the blade or vane exposed to the hot combustion gases. The impingement tubes are hollow tubes that run radially within the blades or vanes. A coolant e. g. air is forced into and along these tubes and emerges through suitable apertures into a void between the tubes and interior surfaces of the hollow blades or vanes. This creates an internal air flow for cooling the blade or vane.
From patent publication EP 1 380 725 A2 an aerofoil with different box- or shell-shaped bodies as impingement devices is known. To fix them in place one of the bodies is brazed to a retaining member and the latter is brazed to the aerofoil.
Problems arise due to a complex and time consuming assembly process and fault positioning of the impingement devices.
EP 1 059 418 A2 and U.S. Pat. No. 4,257,734 A disclose aerofoils with impingement devices. The impingement devices show flutes/corrugations engaging wall grooves at inner walls of the aerofoils to fix them in place.